Telephone system



March 25 1924. 1,487,761

c. SPARKS TELEPHONE SYSTEM Filed June 29. 1918 2 SheetsSheet 1 313 HUnrnEg.

Eharlea Sparks.

c. SPARKS TELEPHONE SYSTEM Filed June 29, 1918 2 Sheets-Sheet 2 2/527 0?. IZYEPZEE 52752125.

Patented Mar. 25, i924.

i 9 iii:

CHARLES SPARKS, OF OAK PARK, ILLINOIS, ASSIGNOB TO KELLOGG- SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Application filed June 29, 1918. Serial No. 242,534.

To all whom it may concern:

Be it known thatI, CHARLES SPARKS, a-

citizen of the United States of America, and

resident of Oak Park, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Telephone Lystems, of which the following is a specification.

My invention relates to telephone systems and has to do more particularly with systems using link or cord circuits for use in completing connections between subscribers telephone lines, and has for its object a novel and improved system ofthe above type. i 7 One of thefeatures of my invention is the provision of means whereby a calling subscriber may automatically-flash his supervisory lamp whenhe wishes to recall, and 0 :1 called subscriber may likewise flash his supervisory lamp when he wishes to recall.

Another feature of my invention is the provision of means whereby a called subscriber is prevented from automatically flashing his supervisory lamp for recall purposes until the calling subscriber has replaced his receiver upon its switch hook.

Another feature of my invention is the provision of automatic means for flashing so the supervisory signals of a link circuit used for interconnecting telephone lines of diiTere-nt character, such as common battery 7 and local battery telephone lines.

Another feature of my invention is-the provision of novel means whereby the operator may answer recalls, under certain conditions. without removing the terminal plugs of the link circuit from the jacks of the connected lines.

These, as well as other features, will be more particularly pointed out in the ensuing specification and in the appended claims.

F or a better understanding of my invenfor the usual supervisorypurposes.

line signals S and S.

The cord circuit C for interconnecting the subscribers A and B ascalling and called lines,.respectively, is provided with an answering plug AP and a calling plug Cl said plugs AP and GP being connected by the heavily marked conductors. The answering end of thecord circuit;- is provided with-a sleeve relay SL energized when the answering plug is inserted into the jack of a calling line. Asupervisory relay SR is also provided, the energizing circuit of which is closed at the switch hook contacts of the calling substation. A listening relay LS is provided, energizcd'upon the actuation of thesleeve relay SL to connect theoperators set 0 and-cord conductors. A recall relay RE is also associated with the answering end of the cord circuit which-is energized when the calling subscriber restores his receiver after termination of conversation to place the cord circuit in condition to allow the calling subscriber to recall, should lie wish to doso. The relay RE is also energized, should the calling subscriber replace his receiver before the called subscriber answers, to prevent further application of ringing currentto the called line. A recall key K is provided, which key when actuated allows the operator to seize the recall. answering meter relay AM and a meter magnet Mlhi are also associated with the answering end of thecord circuit C to register the calls answered by the operator. An answerng supervlsory lamp Allis also provided Associated with the calling. end of energized when the calling'plug OP is inserted into the jack. of the called line. The relay SL', upon energizing, opens the circuit of listening relay LS, which relay then restores, disconnecting the operators set 0 from the cord conductors. ,A party line ring ing key BK is also provided forconecting one of a pluralityof ringing generators G,

G, G and G to signal the subscriber at the called-for substation. A ringing control relay RC is also provided, which relay is the :cord circuit C'is a sleeve relay SL which is energized upon the actuation of the ringing key RK to connect ringing current to the called'line. An interrupter relay IR is also provided which energized upon the actuation of the ringing key to connect ringing current to the called line to give instantaneous first ring to the called-for subscriber. The relay RC also connects the interrupter l to the interrupter relay IR. A ringing trip relay HT is provided which is actuated upon response of the called-tor subscriber, should the called subscriber remove his receiver in response to the call signal during a ringing period. he relay RT, upon deenergizing, interrupts the circuit of the ringing control relay RC and the said relay BC in turn disconnects the interrupter I to allow the interrupter relay Ill to remain at normal. A supervisory relay SR is also provided which is actuated upon the response of the called subscriber to interrupt the circuit of the relay RC, should the called-for subscriber answer during a silent period. A calling supervisory lamp CL is provided, and is used for the usual supervisory purposes. A slow-acting relay 72 is provided which is energized upon the actuation of the supervisory relay SR, and a recall relay RE is also provided, which relay energizes when the called subscriber replaces his receiver, after the termination of a conversation, to place the cord circuit in condition to allow the called subscriber to recall, should he desire to do so. The relay RE duly operates after the calling subscriber has replaced his receiver, for purposes which will be more fully hereinafter described.

Referring now in general to Figure I show a universal cord c cuit G adapted to interconnect telephone lines of dilierent character; for example, to connect common battery and local battery telephone lines, connnon battery and common battery lines, or local battery and local battery lines. In l igure 2, I show a calling common but tcry substation. A and a calling local battery substation A and to the right of the drawing, l show a called common battery substation B, and a called local battery substation B The common battery substations A and B terminate at the exchange in line circuits L and L which comprise the usual line relays Li 2 and LE cut-oil relays CO and CO line signals J ant S and multiple jacks J and J The local battery substations A and B terminate at the exchange in the line circuits L and L respectively, the line circuits L and L comprising the high resistance wound cut-oil relays C6 and CO multiple jacks J and J and drop signals DS and DS.

The universal cord circuit C comprises an answering plug AP, and a calling plug GP, the two plugs being connected by the heavily marked conductors and through the medium of a repeating coil RP, coniprising the windings a, l), and (Z. The answering end of the cord circuit (,1 comprise-s a sleeve relay SE which is actuated when the plug Al is inserted into either a jack a common battery or a local battery line. A switching relay hill is pro-- vided, which relay energizes when the plug AP is inserted into the jack of a conin'iou battery line, the said relay till remaining at normal when the plug All is inserted into the jack of the local battery line due to the high resistance of the winding of the cutoff relay of the local battery line circuit. A supervisory relay SR is provided which is actuated over the line when connection is made with the common battery line. A disconnect relay DR is also provided which is actuated when a local battery subscriber transmits a disconnect signal to the exchange by the operation of his hand generator. A recall relay RE is also provided, which relay RE connects interrupter l to the answering supervisory lamp AL, should the calling common battery subscriber wish to recall. The said relay RE also actuates when the local battery substation sends a disconnect signal which connects the interrupter l with the lamp AL to give the operator a flash disconnect signal. The relay SE is a doublewound relay, the left-hand winding being associated with the answering plug AP, and the right-hand winding being associated with the calling I r'u n 1 plug CP. lhe calling end or the cord circuit G contains similar apparatus to that described in connection with the answering end of the cord circuit C, namely, the switching relay SW supervisory relay SR disconnect relay DR, and the recall relay RE? A listening key Ll; is provided, which, when actuated, connects the operators set 0 to the cord conduc' and a ringing key BK is also provided to connect ringing current to ring the local hattery substation B a called line or to connect any one of the generators G, G. G or G to ring the desired common bai'itery substation as a called line.

Having described in general the preterred arrangement of the circuits and apparatus employed in my invention, I will now describe it more in detail operating in connection with the exchange system illus trated.

Operation of 00rd circuit of Fig. 1.

Referring now more particularly to Fig. 1, and assuming that the subscriber at the calling substation A initiates a call, the removal of the receiver thereat brings about the energization of the line relay LR of the line circuit L, and the actuation of said relay LR brings about the lighting of the line signal S. The operator associated with the cord clrcuit G, noting the lighted line signal S, inserts the answering plug AP of the cord circuit G into the answering jack J of the calling line. The act of inserting the plug AP into the jack J closes a series energizing circuit for the sleeve relay SL of the cord circuit C, and the cut-oft relay C of line circuit L, traced from battery through the windings 2 and 3 of the sleeve relay SL, conductor 4, sleeve contacts of the connected plug AP and jack J, and through the winding of the relay CO to ground. The alternate contact 5 of the relay LS having now closed, a different circuit is established for the sleeve relay SL, traced from battery, through the lower winding 2 of the relay SL, alternate contact 5 of the relay SL, conductor 4, sleeve contacts of the connected plug AP and jack J, and through the cut-off relay CO to ground. The shunting of the upper winding is to provide means for preventing a plurality of operators from connecting to a calling line.

The closing of alternate contact 6 cl relay S L establishes an energizing circuit for the listening relay LS, traced from battery through the upper winding 7 of the relay LS, conductor 8, alternate contact 6 of relay SL, and conductor 9 to ground at normal contact 10 of the sleeve relay SL. The closing of alternate contacts 11 and12 of the listening relay LS connects the operators set 0 to the cord conductors over conductors 13 and 14, through alternate contacts 11 and 12 of relay LS, and over conductors 15 and 16 to the tip and sleeve conductors of the cord circuit C. The closing of alternate contact 17 of relay SL closes a circuit of the supervisory relay SR, traced from battery, through the upper winding of the relay SR, conductor 18, ring contacts of the connected plug AP and jack J, through the substation, back over tip contacts of the connected jack .l and plug AP, conductor 19, alternate contact 17 of relay SL, conductor 20, and through the lower winding of relay SR to ground. The opening of normal contact 21 oi relay SR prevents the premature lighting oi? the answering supervisory lamp AL. The closing of alternate contact 22 of relay SR establishes an energizing circuit for the answering meter relay AM traced from ground at normal contact 23, of relay SL, over conductor 2%, through alternate contact- 22 of relay SR, conductor 25, normal contact 26 of relay AM, through the winding of said relay AM, conductor 14:, alternate contact 12, conductor 16, normal contact 27 of ringing control relay RC, and through the lower winding of the relay SR to battery and ground. The relay AM closes a locking circuit for itself, traced from ground at its alternate contact 26, through the winding of the said relay and over the retardation coil BA to ground.

previously described path to battery and ground, through the lower wlnding of the supervisory relay SE.

The closing of alternate contact 28 of relay AM closes an energizing clrcuit for the meter magnet MM traced from battery,

through the winding of the magnet MM to ground at alternate contact 28 of relay AM.

Magnet MM, upon energizing, steps the regsubstation B that is wanted, the operator tests the multiple jack of the wanted line in the usual manner, by placing the tip of the calling plug GP to the sleeve of the multiple jack J of the wanted line. If the Wanted line is busy, the sleeve of the jack will be at a battery potential, causing a flow of battery through the tip of the plug Cl through the normal contacts 29 of relay 111, normal contact 30 of relay RC, conductor 15, alternate contact 11 of relay LS, conductor 13, through the winding 31 of the induction coil 16, and through the winding 32 of the This induces an impulse of current into the wind ing 33 of the induction coil IC to produce a click in the operators receiver 34, notifying the operator of the busy condition of the line.

Uallccl line z'clle. 3

Assuming that the line is idle, the operator inserts the calling plug GP into the multiple jack J of the called line, closing a series energizing circuit for the sleeve relay SL and the cut-oil relay C0 of the line circuit L, the circuit being traced from battery throughthe winding of the relay SL, condnctor 35, sleeve contacts of the connected plug GP and jack J, and through the winding of the cut-off relay CO'to ground, The opening of the normal contact 10 of relay SL opens the circuit of listening relay LS, said relay LS restoring opens its alternate contacts 11 and 12 to disconnect the operators set 0 from the cord conductors. The opening of alternate contact 12 of re lay LS opens the locking circuit of the answering meter relay All, the said relay restoring to normal. The closing of alternate contact 23 of relay SL establishes an energizing circuit for the calling supervisory lamp CL, traced from battery through the lamp CL, normal contact 36 of relay RC, conductor 37. conductor 38, normal contact 39 of relay RE, conductor 40, normal contact 41 of the ringing trip relay RT, con ductor 42, no 111211 contact 43 of relay SR, and conductor A l to ground at alternate contact 23 of therelay SL. The said supervisory signal CL remains lighted until the called for subscriber is signaled by the operator. The operator now depresses the proper ringing key plunger ol the ring ing key RH to its fully depresed position, which. moves the end spring contacts and 4:6 oi the ringing key RK to their alternate position and connects the proper ringing generator G, G, G or to signal the called for subscriber at substation B. The closing of alternate contact ot the end springs of the ringing key Rh: establishes an energizing circuit for the ringing con trol relay RC, traced from battery through the winding of the said relay RC, condu tor ell, alternate contact 45, conductor 38, norand contact 39 of relay RE, conductor ll), normal contact a l of relay RT, conductor 42, normal. contact 43 of relay SP and conductor let to ground at alternate contact 23 of relay SL. The relay IR is also energized during the interval that the hey is held down over a circuit traced from battery through the lower winding a8, conductor lf), alternate contact 46, and conductor to ground at alternate contact 5]. of the relay EC. The closing of alternate contact 12$) of relay ll connects ringing current from the generator G, which we will assume the selected ringing generator to the called line, giving an instantaneous first ring to the called subscribefis call bell at substation B. The closing of alternate contact 36 ot' relay HQ establishes a locking circuit for the said relay EC, traced from battery through the vinding of the relay RC, said alternate con tact 36, conductor 37, conductor 3c, normal contact 39 of relay RE, conductor :0, normal contact ll of relay RT, conductor 42, normal contact as of relay SR and conductor 44 to ground at alternate contact 23 of relay SL.

The closing of alternate contact of relay RC connects interrupter I to the interrupter relay IR, over a circuit traced from ground. through the constantly rotating interrupter I, through alternate contact o't rleay RC, conductor 53, and through the upper winding 5-} 0i. relay Ill to battery and ground. The relay H1 is thus intermittently energized and (lo-energized to connect ringing cu rrcnt from the generator G over a circuit traced from the ungrounded pole of the generator G, through the alternate contact of the ringing plunger contact, c0nductor 56, through the winding of the ring ing trip relay RT, conductor 57, conductor 58. alternate contact 29 of the relay IR, tip contacts ot the connected plug GP and jack J, through the condenser and call bell 01" the called substation B, through the ring contacts of the jack J and plug OP, alternate contact 59, and through the resistance to battery and ground.

The closing of alternate contact 61 or the relay IR transmits a ringing tone to the calling subscriber at the substation A traced over a circuit extending from the generator G coiuluctor through resistance 65, condenser (3%, alternate contact 61 of relay lll, conductor (35, alternate contact 30 of relay RC, tip contacts of the plug AP and ack J, through. the substation receiver, back through the ring contacts of the jack J and plug AP, over conductor 18, and through the upper winding of the relay SE to bat tery, giving the calling subscriber at the substation A an audible signal, notifying him that the called subscriber is being signaled. The called subscriber at the substation B is thus automatically signaled until the called subscriber at the substation B answers in response to his call signal, or until the calling subscriber replaces his receiver. The non-inductive winding N which is in multiple with the winding of the ringing trip relay HT is only connected to the low frequency of the ringing current, say the 16 cycle ringing current. Should the operator have depressed the ringing key ilungcr to connect the ringing generator it", which we will say is the generator delivering 16 cycle ringing current, the said current will pass through the closed contacts of the ring in plungers from generator G to the point 66, the current then dividing, part passing over conductor 67, through alternate contact 68, through the resistance lV, over conductors 5'? and 58 and alternate contact 29 of relay IE to the call bell at the called substation, and back to battery and ground at alternate contact 59 of relay Ill, while tle other path which divides at point 66 passes over conductor 56, through the winding of relay RT, to battery and ground at alternate contact of relay 1R, as before described. lVithout this resistance W, should the low frequency current pass through the relay ET, the said relay might chatter, and 'pen. the locking circuit of the ringing control relay RC at contact ll, which would bring about the premature disconnect-ion ot the ringing current from the called line. The winding ll in multiple with the winding of the relay PT prevents this chatter ol the relay RT.

Should the subscriber at the called substation B answer during a silent period, that is, when the relay IR is in a de-energized condition, a circuit is closed through the supervisory relay SR, traced from battery through the lower winding of the said relay SR, normal contact 59 of relay IR, the ring contacts of the connected plug GP and jack J, through the now closed contacts ot' the substation switch hook, back through the tip contacts of the connected jack J and plug GP, normal contact 29 of relay IR, conductor 69, alternate contact 70 of relay Slit, conductor 71, and through the upper winding of the relay SR to ground. The opening of normal contact 13 of the relay SR opens the locking circuit of the ringing control relay RC, which relay de-energizes to open its alternate contact 52, and the opening of said contact 52 disconnects the constantly rotating interrupter I from the upper winding 5 1 of the relay IR. The said relay RC now restores to normal, thus preventing the ringing current from being: applied to the subsCribefls line.

Should the called subscriber at substation B answer during a ringing interval, the ringing current is interrupted, due to the combined generator and battery flow through the ringing trip relay RT, which relay now operates over a circuit traced from the ungrounded pole of the generator G, alternate contact 55, conductor 56, through the winding of the said relay RT, conductors 57 and 58, alternate contact 29 of relay IR, the tip contact of the connected plug CP and jack J, through the now closed contacts of the substation switch hook back through the ring contacts of the connected jack J and plug CP, through alternate contact 59 of relay IR, and through resistance 60 to battery and ground. The disconnection of the condenser at the substation permits the battery flow through the winding of relay RT to bring about the energization of the said relay RT. The relay RT energizing, opens its normally closed contact -11 to interrupt the locking circuit of the relay RC. The said relay RC restoring, opens its alternate. contact 52 to disconnect the ringing interrupter I to prevent further application of ringing current to the. called line.

The closure of normal contacts 29 and 59 of relay IR brings about the energization of the supervisory relay SR, as previously described. Upon the restoration of the relay RC and upon the energization of the supervisory relay SR, a portion of the batterv flow through the calling supervisory lamp CL flows through the winding 7 3 ot the relay 72 to bring about its energization, the circuit being traced frombattery through the lamp CL, normal contact 36 of relay RC, conductors 37 and 38, normal contact 39 of relay RE, conductor 10, normal contact 11 of relay RT, conductor 42, the alternate contact #13 of relay SR. conductor 7 1, normal contact 75 of. relay 72, the lower winding 73 of relay 72. conductor 76, conductor 77, normal contact Z of the key K, and conductor 79 to ground at alternate contact 10 of the sleeve relay SL. The battery flow through the lower winding of the relay T2 is sufficient to bring about the actuation of the said relay 72, which relay now closes a locking circuit for itself, traced from b'attery through the upper winding 80 of the said relay 72. its alternate contact 75, the lower winding 73, conductors 76 and T7,

normal contact 78 of key K, conductor 7 9 to ground at alternate contact 10 of relay SL, for purposes as will be more fully hereinafter described.

The calling and called subscribers':=,A and B are now connected in conversational circuit, the talking circuit being traced over.

the heavily marked conductors. Should the calling subscriber at substation A restore his receiver before the called subscriber answers, the supervisory relay SR restores due to the opening of the switch hook contacts at the calling substation A. The closing of normal contact 21 of relay SR establishes an energizing circuit for the recall relay RE, traced from battery through the upper winding of the said relay RE, conductor 81, alternate contact 82 of relay SL, and conductor 83 to ground at normal contact 21 of relay SR. The closing of alternate contact 84 of relay RE establishes a locking circuit for itself, traced from battery through the lower winding of the said relay RE, alternate contact 8 1, conductor 85, normal contact 86 of key K, conductor 79, to ground at alternate contact 10 of relay SL. The opening of normal contact 39 of the recall relay RE opens the locking circuit of the ringing control relay RC, which relay restores to open its alternate contact 52 to disconnect the ringing interrupter I, permitting the restoration of the interrupter relay IR. The said relay IR restoring prevents further application of ringing current to the called substation B.

The closing of normal contact 21 establishes an energizing circuit for the answering supervisory lamp AL, traced from battery through the lamp AL, alternate contact 82 of relay SL, and conductor 83 to ground at normal contact 21. The closing of alternate contact 39 of relay RE establishes an energizing circuit for the supervisory lamp CL, traced from battery through the said lamp, conductor 87, alternate contact 39 of relay RE, conductor 10, normal contact 41 of relay RT, conductor 42, normal contact 43 of relay SR, and conductor 14 to ground at alternate cont-act 23 of relay SL. The two supervisory lamps AL and CL being lighted, indicate to the operator that the calling subscriber has replaced his receiver and disconnection may take place.

Discormcctirm.

After the subscribers have finished conversation, they replace their receivers upon their respective switch hooks, causing the supervisory relays SR and SR to restore. The restoration of the relay SR causes its normal contact 21 to establish an energizing circuit for the recall relay RE over a circuit as above described, and the restoration of the supervisory relay SR closes an energizing circuitfor the recall relay RE. over a Circuit traced from battery through the upper winding of the relay RE, alternate contact 88 of relay 72, conductor 89, the alternate contact of relay RE, conductor 91, alternate cont-act 92 of relay SL, conductor 93, normal contact 43 of relay SR, and conductor 44 to ground at alternate contact 23 of relay SL.

The relay RE, upon energizing, establishes a locking circuit for itself, traced from battery through the lower winding of" the said relay RE, its alternate contact 94, conductors 76 and 77, normal contact 78 of key K, and conductor 79 to ground at alternate contact 10 of the sleeve relay SL. The energizing circuits for the answering supervisory lamps AL and CL are also established as previously described, and the operator, noting the two lighted signals, removes the plugslXP and GP from their respective jacks J and J. The removal of the plug AP from the jack J opens the series circuit of the cut-off relay CO and sleeve relay SL. The sleeve relay SL restoring, opens the locking circuit of the relay RE, and theremoval of the plug GP from the jack .l

opens the series circuit of the cut-off relay CO' and the sleeve relay SL. The opening 01 the alternate contact i0 of relay SL opens the energizing circuits of the relay 72 and the recall relay RE. The cord circuit C is now at normal and is available for establishing other connections.

" Recall by caZZing subscriber.

Assuming that the subscribers have linishcd conversation and before the plugs AP and GP have been withdrawn from the jacks, that the calling subscriber wishes to recall, the removal of the receiver at the substation A again closes an energizing circuit tor the supervisory relay SR, through the closed contacts at the substation switch hook. The relay RE having been energized as before described, its alternate contact is closed to connect the constantly rotating interrupter I with the answering supervisory lamp AL, the circuit being traced from ground through the constantly rotating interrupter I, conductor 96, alternate contact 95 of relay RE, alternate contact 21 of the now energized relay SR, conductor 83, alternate contact 82 of relay SL, and through the answering supervisory lamp AL to battery. The answering supervisory lamp AL is caused to flash, due to the in terrupter 1, giving the operator atthe cord circuit C a. flashing recall signal, notifying her that the subscriber at the substation A Wishes'to recall. The operator noting the flashing signal actuates her recall key K to bring about the energization of the listening relay LS over a circuit traced from battery through the lower winding of the relay LS conductor 97. the'alternate contact. 98 or the key' 'K, conductor 99, normal contact as of the relay SR, and conductor 44: to ground at alternate contact 23 of relay SL. The relay LS again energizes to close its alternate contacts 11 and 12 to connect the operators set 0 to" the cord conductors, and the operator now inquires the wants of the recalling subscriberi at substation A. The opening of the normal contact 86 of the key K opens the locking circuit of the recall relay RE, the said relay RE restoring to normal opens its alternate contact 95 to disconnect the interrupter I from the answering supervisory lamp AL to prevent further flashing of the said supervisory lamp AL. The opening of normal contact 78 of the key K brings about the de-energization of the relay 72 and recall relay RE.

If another subscriber other than B is wanted by the recalling subscribe-r at substation A, the operator removes the calling plug CP from the connected'jack J and inserts it into another jack of the wanted line. The calling plug CP having been re moved, the relay SL restores to normal, opening its alternate contact 23, which brings about the de-energization of the listening relay LS which disconnects the operators set 0, and another insertion of the plug CP into another jack allows the circuit to be operated as previously described.

Recall by called subscriber.

Assuming that the called subscriber at the substation B wishes to re all after the subscribers have replaced their receivers upon their respective switch hooks, the removal of the receiver by the subscriber at the substation B brings about the energization of the supervisory relay SR through the now closed switch hook contacts of the recalling substation. B. The relays 72 and RE having been energized as previously described, the interrupter I is connected through to the calling supervisory signal CL, the circuit being traced trom ground through the constantly rotating interrupter I, conductor 100. alternate contact 101 of the relay RE, conductor 74, alternate contact 48 of relay SR, conductor 42, normal contact ll of relay RT, conductor 40, alternate contact 39 of relay RE, (the relay RE having been energized upon the restoration of the receiver at the calling substation A,) conductor 87, and through the lamp CL to battery. The lamp GL is flashed by the interrupter I, and the operator noting the flashing signal CL knows that the called subscriber at the substation B is recalling. The operator now actuates her key K to bring about the energization of the listening relay LS, the circuit being traced from battery through the upper winding of the relay LS. over conductor 8, alternate contact 6 of relay SL. conductor 102. alternate contact 103 of the key K, and conductor 1% to ground at normal contact 2101' the relay SR, the said relay SR having restored when the calling subscriber at substation A replaced his receiver. 7

The closing of alternate c0ntacts 10 and 11 ot' the relay LS again connects the operators set 0. to the cord conductors to inquire the wants of the recalling subscriber at the substation B.

The opening of normal contact 78 of the key K brings about the de-energization of relay 7 2 and recall relay RE, and the open ing of alternate contact 101 of relay RE opens the circuit of the supervisory lamp CL to prevent further flashing of said lamp, and

the operation of the apparatus in re-e-sta-blishing a connection for the subscriber at noted that the called subscriber at substation B may only recall after the calling subscriber at substationvA has replaced his receiver upon the switch hook, so that shouldthe called subscriber at substation B in answering a call fumble his'receirer in removing it from the switch hook, thereby ac,- cidentally closing the switch hook contacts and then again opening them, and finally closing them in answering a call, the flashing of the calling supervisory lamp CL will not be established, due to the fact that the recall relay RE associated with the answering end of the cord circuit C has not been actuated, and as alternate contact 39 is not closed the calling supervisory'lamp is not affected so that a false recall signal will not be sent.

Operation of Figure 2.

In Figure 2, I show a modified form at my invention in the form of a universal cord circuit in which either the calling or called local battery subscribers may initiate a flash disconnect signal upon the termination of conversation and in which a calling or a called common battery subscriber may initiate a flash recall after termination of conversation. he cord circuit is also ar: ranged so that an operator can distinguish between a disconnect and a recall signal.

Assuming now that the common battery subscriber at the substation A initiates a. call, the removal of the receiver there-at establishes an energizing circuit for theline relay LE which relay, upon energization, brings about the lighting of theline signal S The operator noting thelighted signal s 'throws her listening key LK'to connect her operators set 0 to the cord conductors of the cord circuit C, and inserts the answering plug AP into the jack J of the calling line. A series energizing circuit is established for the cut-off relay CO"; the sleeve relay SE and the switching relay SW,

' this circuitbeing traced from battery through the winding of the switching relay SW, conductor 105, winding 106 of the relay SE, conductor 107 sleeve contacts of the connected supervisory relay SE to the cord conductors, which relay SR now operates over the linethrough the closed contacts of the substation switch hook. The closing of alternate contact 110 of the relay SR establishes an energizing circuit for the relay 111, traced from battery through the winding of the said relay 111, and conductor 112, to ground at alternate contact 110 of relay SR The opening of normal contact 113 of relay 111 prevents the premature lighting of the answering supervisory lamp AL.

Common battery to common battery.

The operator now inquires the wants of the calling subscriber, and assuming that it is the subscriber at the common battery substation B that is wanted, the operator tests the multiple jack J 3 of the calledline in the usual manner, and assuming that the line is idle, she inserts the calling plug GP into 1 the jack J of the called line to close a series energizing circuit for the cut-off relay CO and switching relay SlV, the circuit being traced from battery through the winding of the switching'relay SlV, conductor 114C, winding 115 of relay SE, con

ductor 116, sleeve contacts of the connected plug C1 and jack J and through the winding of cut-offrelay CO to ground. The

- switching relay SWV and the cut-off relay C0 are thus energized in series. The relay SEis held energized, it having been energized upon the insertion of the answering plug AP into the jack J of the calling line. The closing of alternate contact 117 of switching relay SW establishes an energizing circuit for the calling supervisory lamp CL, traced from battery through normal contact 118 of relay 111, conductor 119, alternate contact 117' of relay SW, 1 and through the lamp CL to ground'at normal contact- 120 of the disconnect relay DR, said lamp CL remaining lighted untilthe called subscriber at substation. B" answers. The operator now depresses the proper ringing plunger of the ringing key BK to connect one of the generators G G G or G of the proper frequency to ring the call bell of ringing current to the called line the tip contacts oi? the connected plug Cl and jack J through the condenser and call bell at the substation B back through the ring contacts of the connected jack J and plug Cl and through alterntae contact 123 of the ringing key RK to ground. The call bell of the called substation B is thus actuated each time; the key RK is actuated and upon the response of the called subscriber at substation B a circuit is estab lished for the supervisory relay SPJ traced from battery through the lower Winding of the said relay alternate contact 12% of relay SYN, normal contact 123 of the ringing key RK ring contacts of the connected plug Cl and jack J through the now closed contacts of the substation switch hook, back through the tip contacts of the connected plug UP and jack J normal contact 122 of ringing key Eli through alternate contact of relay Sil and through the upper winding of relay SR to ground. The closing of alternate contact 12-6 of relay SR" establishes an energizing circuit for the relay 111 traced from battery through the winding of the said relay 111 and conductor 127 to ground at alternate contact 126 oi relay SR The opening of normal contact 118 of relay 1 .1 eilaces the supervisory signa Cal no ying the operator that the called subscriber at the substation B has answered. The subscribers are now in conversational circuit, the said talking circuit being traced over the heavily marked conductors.

Assuming that the subscribers have finished conversation, they replace their receivers upon their respective switch hooks at the substations it and .13.

1. me replacing oi the receiver at the substation A brings about the de-energization of the supervisory relay The opening of alternate contact 110 of relay SR opens the energizing circuit for the relay 111. but the relay 111 being slow to release, holds its alternate contact 128 closed momentarily, bringin about the energization of the recall relay R13 traced from battery through the winding of the said relay RE normal contact 129 of: relay R conductor 130. and alternate contact 1 8 to ground at normal contact 110 of r lay SP3. The relay RE upon energizig, establishes a locking circuit for itself traced from battery through the winding ot the said relay its alternate contact 129, conductor 131 and through alternate contact 132 of relay SE to ground at normal contact 133 of listening key LK. The replac ing of the receiver at the called substation 13 brings about the de-energization of the supervisory relay SR and the opening of alternate contact 126 of the relay SR opens the energizing circuit of the relay 111, but the relay 111 being slow to release its alternate contact 134 is momentarily held closed to establish an energizing circuit for the recall relay 3E over a circuit traced from battery through the winding of the recall relay 3E normal contact 135 of relay RE conductor 136 and alternate contact 134- c The closing of normal contact 113 of relay 111 brings about the lighting of the answer ing supervisory lamp AL over a circuit traced from battery through said normal contact 113, conductor 137' alternate contact 138 of relay SW and through the lamp ill to ground at normal contact 139 oi the relay DR.

The closing of normal contact 118 of relay 111 closes a circuit for the calling supervisory lamp CL, traced from battery at said normal contact 118, over conductor 119, through alternate contact 117 through calling supervisory lamp CL, to ground at normal contact 120 of relay DR. The operator noting the two lighted supervisory signals AL and CL, knows that conversation has been terminated, and withdraws the plugs AP and Cl from their respective jacks J and J The withdrawal of the plug AP from the jack J allows the relay SW of the cord circuit C and the out if relay C of the line circuit L to restore. The removal of the plugs P from the ack J allows the switching relay SW the relay, SE, and the cut-ofi' relay CO to restore, and the opening of alternate contact 132 of relay Si l opens the locking circuits of the recall relays RE and R13 The apparatus of cord circuit C is now at normal and available for establishing other connections.

Assuming that conversation has terminated, and, before the plugs Al and Cl? have been withdrawn from their respective I jacks, the subscriber at the substation A wishes to recall, the removal of the receiver at the substation A again energizes the supervisory relay SR over the line and the closing of its alternate contact 110 establishes an energizing circuit for the relay 111. As the relay RE is energized upon the subscriber at substation A. replacing his re ceiver, the constantly rotating interrupter I is no connected to the answering supervisory lamp AL over a circuit traced from ground through normal contact 139 of relay DR, through the lamp AL, alternate cont-act 138 of relay SW, conductor 137,

alternate contact 113 of relay 111, conductor 140, through alternate contact 1&1 of relay RE and through the interrupter 2 to battery and ground. The lamp AL is thus flashed, due to the constantly rotating interrupter I and the flashing slgnal notities the operator that the calling subscriber A wishes to recall. The operator now actuates her listening key LK to connect her operators set C to the cord conductors to inquire the wants of the recalling subscriber at sub-station A, and upon the actuation of the key LK, normal contact 133 is interrupted to open the locking circuit of the recall relay RE which relay restores to open its alternate contact 141 to disconnect the interrupter I to prevent further flashing of the answering supervisory lamp AL.

t a subscriber other than the subscriber B is wanted by the recalling subscriber at substation A, the operator withdraws the plug CP from its connected jack and inserts it into the jack of the now wanted subscriber. The removal of the plug CP' from the jack J allowsrelays SW, SE and CO to restore, and the operation of the apparatus in establishing another connection is readily apparent.

Assuming that the called subscriber at substation B recalls, the removal of the receiver at the substation B again brings about the energization of the supervisory relay SR over the line, and the closing of alternate contact 126 of relay SR brings about the energization of the relay 111, and the closing of its alternate contact 118 now. connects the constantly rotating interrupter I in circuit with the calling supervisory lamp CL, said circuit being traced from ground at normal contact 120 of relay DR through the lamp CL, alternate contact 117 of relay SVV', conductor 119, alternate contact 113 of relay 111, conductor 142, through alternate contact 1 13 of the recall relay RE? conductor 144. and through the rotating interrupter I to battery and ground. The calling supervisory lamp CL is thus flashed, and the flashing signal CL notifies the operator that the subscriber at the substation B is recalling. The operator now actuates her listening key Li: to connect her operators set 0 to the cord conductors and inquires the wants of the recalling subscriber at the sbustation B. The opening of the normal contact 133 of the listening key LK opens the locking circuit for the recall relay RE The said relay RE restores and opens its alternate contact 143 to disconnect the interrupter 1 thereby.

preventing further flashing of the calling supervisory lamp CL, The method of establishing another connection for the recalliu subscriber at substation B is readily apparent and further description is not necessary.

station A initiates a call, the actuation of establishes a series energizing circuit for the cut-off relay CO and the'sleeve relay SE of the cord circuit C, said circuit being traced from battery through the winding of the switching relay SW, over conductorv 105, winding 106 of relay SE, conductor 107, sleeve contacts of the connected plug AP and jack J and through the winding of the cut-off relay CO to ground. The cut-cit relay CC and sleeve relay SE are actuated, but due to the high resistance of the cut-oil relay C0 of the local battery line circuit L, the switching relay SW fails to operate and remains at normal. The operator now actuates her listening key LK to connect her operators set C with the cord conductors and inquires the wants of the calling subscriber, and assuming that it is the local battery subscriber at substation B that is wanted, the operator. tests the line in the usual manner. Assuming that line B is idle, the operator inserts the answering plug CP into the jack J oi: the wanted line. A circuit for the cut-off relay CO or line circuit L may be traced from battery through the winding of the switching relay SW, conductor 114:, winding 115 of relay SE, conductor 116, sleeve contacts of the connected plug CP and jack J and through the winding of the cut-oii relay CO to ground. The switching relay SlV does not operate due to the high resistance of the cut-oii relay CO and remains at normal, the sleeve relay SE having been already energized when the plug AP was inserted into the jack J of the calling line. The operator now actuates the ringing key RK to connect the ringing generator G to ring the call bell of the called-for subscriber at substation B the path for the ringing current being traced from the ungrounded pole of the generator G through the normal series contact of the ringing key BK to alternate contact 122 of the ringing key RK tip contact of the connected plug CP and jack J through the call bell of the substation B back to the ring contacts of the connected jack J 5 and plug CP tog-round at alternate contact 123. The operator thus rings the call bell at the substation B until the called subscriber thereat answers. Assuming that the subscriber has answered, the conversational circuit may be traced over the heavily marked conductors.

Assuming that the subscribershave finished conversation, the subscribers at the substations A and B restore their receivers upon their respective switch hooks and ac tuate their hand generators to give the dis connect signal to the operator of the cord circuit C. The sub lcriber at substation A having actuated his hand generator, current will pass through the disconnect' relay DR of the cord circuit C, the circuit being traced from the hand generator at substation A over the tip contacts of the jack 3* and plug AP, normal contact 108 of re lay SW, through the windin of relay DR, normal contact 109 of relay SW ring cone tacts of the connected plug AP and jack J bacl; to the generator of the substation A When current passes through the disconnectrelay DR-glt closes its alternate con tact 139, bringing about the energization of the recall relay RE traced from battery through the winding of relay RE and no mal contact 139 of relay RE to ground at alternate contact 139 of relay DR.

,The closing of alternate contact 129 of relay RE establishes locking circuit for said relay RE as previously described, and when the subscriber at substation A has ceased actuating his hand generator, relay DR restores to normal. The closing or" al ternate contact 141 of relay RE connects the interrupter I to the lamp AL, the circuit being traced from battery through the interrupter 1 through alternate contact 141, conductor 140, normal contact 138 of relay SW1 and through the lamp AL to ground at normal contact 139 of relay DE. The lamp AL is flashed due to the interrupter I giving the operator of the cord circuit C, a flashing disconnect signal, or if code signals have been arranged, the subscriber at the substation A may actuate his generator according .to a certain code and :notifvithe operator at the cord circuit C whether the flashing signal is either a disconnect signal or a recall signal.

The operator noting the flashing signal actuates her listening key LK to interrupt the normal contact- 133, should the flashing s 'ual beira recall, and the opening of its contact 13-3 interrupts the circuit of relay RE to open its alternate contact 141 to prevent further flashing of the signal AL.

Assuming that the subscriber at the local battery substation B actuates his hand generator after finishing conversation. the;current tronnthe hand generator actuatcs the disconnect relay DR, is apparent from the previous description in connection with relay DR.

The closing of alternate contact 120 of relay DR establishes a circuit for the recall relay traced from battery through the winding of said relay. normal contact 135 of relay R13 and. through alternate contact 120 of relay DR to ground. and the closing or". alternate contact 125 of relay establishes a locking circuit for the said relay BB to ground at normal contact 138. i

Viheu the subscriber att-he substation B has finished sending a disconnect signal, the

relay DR restores to normal, closing the circuit for the calling supervisory lamp CL, traced from ground at normal contact l20 of relay DR through the lamp CL, normal contact- 117 of SW; alternate contact lal3 conductor 144:, and through the interrupter I to battery and ground. The calling supervisory lamp CL is caused to flash, due to the constantly rotating interrupter 1 to give the operator a flashing disconnect signal, or in case of a code signal to signal the operator for a recall. In answering a recall, the operator actuatcs the listening key LK to connect her operators set Oto the cord conductors. The open;- ing of normal contact 133 ot the hey LK opens the locking circuit of the relay RE, and the opening of the alternate contact 143 of relay RE disconnects the interrupter 2 and the calling supervisory lamp CL to prevent further flashing of the said'lainp. Common battery 2 0 locallbatzfery,

Should; a calling common battery subscriber at the substation A wish to converse with the local battery subscriber at substation E the insertion of the plug AP into the jack J brings about the energization of the relays CQ SE, and switching relay' SW, as previously described, and the closing of alternating contacts 108 and 109 of relay Si l brings about the actuation of the supervisory relay SR over the line. The operator in inserting the ecalling plug GP intorthe jack J of the local battery line B brings about theenergization of the cutoff relay CO traced fromibattery through the switching relay SlV to ground. This circuit also passes through the winding 115 of the relay SE. The switching relay SVV does not operate when connected to the local battery line for reasons as previously described. The calling subscriber at the substation A may recall after replacing his receiver upon his switch hook in the manner as previously described, and the local battery subscriber at the substation B may transmit a flashing disconnect signal to the operator of the cord circuit C, as is readily apparent from the previous description.

The subscriber at local battery substation A when calling actuates his;drop signal DS, and the operator in response thereto inserts the answering plug AP into the jack J of the calling line. In this nstance, the cutofit relay C0 and the sleeve relay SE are actuated through the switching relay SW to battery. The switching relay SW does not operate due to the high resistance of the cut-ofi' relay CO Should the com mon battery substation B be wanted, the operator inserts the plug CP into the jack J of the called line, and this act brings about a series energizing circuit for the cut-oil relay CO and the switching relay cit SKV, the relay SE having been energized when the answering plu APwas inserted intothe jack J of thecalling'local battery line. The disconnect signal 'from the local battery calling substation A is the same as previously described, and the discminect signal from the called common battery substation B is the usual lighted supervisory signal ;CL andshould the called subscriber B initiate arecallthe operation of the apparatus used in establishing this recall is the same as previously described.

While I have illustrated several forms of my invention, I do not-wish to be limited to the same asvarious other arrangements may readily suggest themselves to those skilled in the art, and I, therefore, wish to cover all such changes and modifications as come withinthe spiritand scopeof the appended claims.

hat I claim as new and desire to secure byUnited States Letters Patent is 1. A telephone system including a'calli-ng and a called suloscribers telephone line, a link-circuit provided with an answering and a calling terminal forconnecting said lines, an oper'ators telephone for said link circuit but normally disconnecting therefrom, automatic means for connectingand disconnecting said operators telephone and said link circuit, said means also serving to prevent more than one operator'from answering the same call at the same time, a supervisory signal associated with said calling terminal, subscriber-controlled means 'torcausing a continuous operation of said signals, automatic means including a relay for flashing said answering signal, automatic means including ,a second relay for fiashingsaid calling supervisory signal, a third relay, and circuits for said first and second relays controllable by vsaid third relay. 7

2. A telephone systemincluding apair of subscribers telephone lines, a link circuit provided with answering and calling terminals for connecting said lines, an answering and a calling supervisory signal for said link circuit, subscriber-controlled means for causing a continuous operation of said answering supervisory signal, a recall relay for connecting a vcircuit interrupter to said a11- swering signal, a second relay tor connecting said circuit interrupter to said calling signal, a third relay having a circuit including a contact of one o't-said terminals, and contacts controllable by said third relay ccntrolling circuits for said first and second el y 3. A tele hone system including a pair of subscriberf telephone lines, a "link circuit provided with an'answeringterminal and a all ng terminal for sme cs Said lines, an operator s telephone for said link circuit but no mally lis nnnec inst o au matic means for connecting and disconnecting said operators'telephone and said link circuit, said means also serving to prevent more than one operator from answering the same call .at the same time, an answering supervisory signal and a calling supervisory signal for said link circuit, subscriber-controlled means for causing a continuous operation of said calling supervisory signal, a source of interrupter current, a relay for connecting said source to said first signal, a relay for connecting said source of current to said second signal,v and circuits for said relays controllable by a' third relay.

4. A telephone system including a pair oi subscribers telephone lines, a link circuit provided with an answering terminal and a calling terminal for connecting said lines, an operatorls telephone for said link'circuit but normally disconnecting therefrom, automatic means for connectingand disconnecting said operators telephone and said link circuit, said means also serving to vprevent more than one operator from answering the same call at the same time, an answering supervisory signal and acalling supervisory signal for said link circuit, a source of current, means for connecting said source of current in circuit with said signals to cause a continuous operationthereot, a source of interrupter current, a relay for connecting said source to said first signal, a relay for connecting said source of current to said second signal, circuits for said relays controllable by a third relay, and a circuit for said third relay including .a contact of one of said terminals.

5. A telephone system including a calling subscribers telephone line, a called subscribers telephone line, a link circuit for connecting said lines, an operators telephone, automatic means for connecting and disconnecting said operators telephone and said link circuit, an answering supervisory signal and a calling supervisory signal for said link circuit, a source of current, subscriber-controlled means for connecting said source of current in circuit with said supervisory signals to cause a continuous'operation thereof,

a source of interrupter current, automatic means for connecting said source of current to said answering signal, and automatic means for connecting said source of current to said calling signal, said last means being operable only when the calling subscriber has first replaced his receiver,said first automatic means also serving to prevent more than one operator from answering the same call at the same time, and also to close contacts in the circuit of the automatic means connecting said source of inte'rrupter current to said answering'si-g-nal.

-6 .VA*telephonc system including a pair of telephone lines. a link circuit for con.- necting said lines conversational circuit, an operators telephone, automatic means all) for connecting and disconnecting said operators telephone and said link circuit, automatic ringing means for signaling the called one of said subscribers lines, operator-controlled means for initiating the operation of said automatic ringing, an answering signal and a calling signal for said link circuit, a source of interrupter current, automatic means for connecting said source of current to said answering signal, and au tomatic means for connecting said source of current to said calling signal, said last means being controlled by both said calling and said called subscribers, said first automatic means also serving to prevent more than one operator from answering the same call and also to close contacts in the circuit of the automatic means connecting said source of current to said answering signal;

7. A telephone system including a pair of subscribers telephone lines, a link circuit for connecting said lines in conversa tional circuit, automatic intermittent ringing means, operator controlled means for initiating the operation of said ringing means and for insuring that ringing current is applied to the called line at the moment the operator controlled means is actuated, means controlled by the calling subscriber for automatically disconnecting said ringing means and said link circuit, a calling supervisory signal for said link circuit, a source of interrupter current, and automatic means for connecting said source of current in circuit through a contact controlled by said ringing disconnect means with said calling supervisory signal, said last means being dependent upon the disconnection of said ringing means and said link circuit and also upon the calling subscriber having signaled for disconnection or recall and the called subscriber having signaled for a call.

8. A telephone system including a calling subscribers telephone line and a called subscribers telephone line, a link circuit for connecting said lines, an operators telephone, automatic means for connecting said operators telephone to said link circuit when the link circuit is connected to the calling subscribers line, automatic means for disconnecting the operators telephone from the link circuit when the link circuit is connected to the called line, a supervisory signal for said link circuit: automatic means for flashing said supervisory signal, said automatic means being operative only after said calling subscriber has signaled tor disconnection or recall and said called subscriber has signaled for a connection, said last automatic means controlled over circuits controlled by the automatic means for connecting and disconnecting said operators telephone and said link circuit.

9. A telephone system including a calling subscribers telephone line and a. called subscribers telephone line, a link circuit for connecting said lines, automatic ringing means for said link circuit, a signal for said link circuit, a circuit for said signal adapted to be closed when link circuit is connected to the called line, means for opening said circuit when the automatic ringing means is associated with the called line, a supervisory relay for said link circuit controlled by said calling subscriber, a supervisory relay for said link circuit controllable by said called subscriber, and means for automatically flashing said signal, said means being controllable by both of said supervisory relays.

10. A telephone system including a calling subscribefis telephone line and a called sub scribers telephone line, a link circuit for connecting said lines, automatic ringing means for said link 0' "cuit, a signal tor said link circuit, said signal adapted to glow when the link circuit is connected to the called line and adapted to be extinguished when said automatic ringing means is operated, a supervisory relay for said link circuit controlled by said calling subscriber, a supervisory relay for said link circuit controllable by said called subscriber, means for automatically flashing said signal, said last means being operable only when said 'answering supervisory relay is operated to signal for disconnection or recall and said calling supervisory relay is energized.

11. A. telephone system including a pair of subscribers telephone lines, a link circuit for connecting said lines, an operators telephone, electromagnetic means for connecting and disconnecting said operators telephone and said link circuit, a supervisory signal for said link circuit, means for automatically flashing said supervisory signal controllable by one of said subscribers, said means being inoperative to flash said supervisory signal unless the other of said subscribers has replaced his receiver, said electromagnetic means controlling contacts in the circuit of said supervisory signal and said last means, and operator controlled means for actuating said electromagnetic means when answering a recall.

12. A telephone system including a pair of subscribers telephone lines, link circuit for connecting said lines, automatic ringing means for signaling one of said subscribers lines, a supervisory signal for said link CllClllC,ll'lBllS for automatically flashing said supervisory signal controllable by one of said subscribers, means controllable by the other of said subscribers for preventing said first subscriber from causing said supervisory signal to be flashed, an operators telephone, electromagnetic means for connecting said operators telephone to said link circuit when the operator answers a recall, and automatic means controlled by the calling subscriber to disconnect ringing current from the called line, and to operate means to signal for a disconnection prior to the response of said called subscriber.

13. A telephone system including a pair of subscribers lines, a link circuit connecting said lines, automatic means for said link circuit for preventing more than one link circuit from connectingto a subscribers line, a signa-l'for said circuit, means for automatically and intermittently operating said signal controlled over one of saidtelephone lines, the operation of said means controlled by the operation of said automatic means, andmeans controlled over the other of said telephone lines for controlling said first means.

14. A telephone system including a calling and a called subscribers telephoneli'ne, a link circuit for connecting said lines, other link circuits, automatic means :to'rpreventing more than one of said link circuits from connecting to said calling sub'scribers telephone line when attempting to answer a call, an answering and a calling supervi'sory signal for said link circuit, automatic means including a double-wound relay "for flashing said answering signal, the initial operation of said automatic means fo'rfiashing said answering signal controlled by said first automatic means, and automatic means including a second double-wound relay 'for flashing said calling signal.

15. A telephone system including a calling and a called subscriberstelephoneline, a link circuit for connecting said lines,-automatic m'elans for said'lin'k circuit-tor preventing more than one link circuit from: being ope'ratively connected'to'a subscribers line at the sametimaautomatic ringing means for said link circuit, an answering and a calling supervisory signal for said link circuit, automatic means "including. adouble-wound relay forfiashing said answering signal, said double-wound relay controlling the operation of said automatic ringing means, automatic means including a second double-wound relay for flashing said calling signal, said first automatic means' controlling contacts in the circuits of said double wound relays, a third relay,- and a circuit for said relays controlled by said third relay.

16. A telephone system including a pair of subscribers telephonexlines, a circuit :for connecting said lines, an answering, and a calling supervisory signal for said circuit, circuits for said signals, a double-wound recall relay for connecting a circuit interrupter to said answering signal, a second double-wound recall relay for connecting said circuit interrupter to said calhng signal,,energizing circuits for said recall relays, an operators telephone, electromagfor connecting saidlines, other link circuits,

and automatic means for preventing connection at one tune of more than one of said link circuits to a calling one of said telephone lines, an answering and a calling supervisory s gnal for said circuit, a doublewound recall'relay for connecting a circuit interrupter to said answering signal, said double-wound relay controlled over a circuit primarily controlled by saidautomatic 'means, a second double-wound recallrelay for connecting said circuit intermpter to said calling-signal, a third relay, contacts controllable'b-y sai'd'third relay controlling the circuitsof said first and second relays.

l8. A-telephone system including a pair 'of'lines, a circuit-torconnecting said lines,

a pair of signals associated said circuit,

:a source of-interrupter current, a doublewound relay for connecting said source of current to one o l-said signals, said relay being provided with an operating winding Vanda lockingwindingand asecond doublewound relay for connecting, said source of current the other ofsaid signals, said: last relay bemgprovided with 'an operating winding and a locking winding said second double-wound relay being inoperative until the first of said relays isoperated.

'19. A a telephone system including a pair of subscriberstelephone lines, a link circuit provided with answering and calling terminalslfor connecting said lines, an operators telephone, automaticelectromagnetic means for connecting and disconnecting said operators telephone and said link circuit, an

answering and a calling supervisory signal for said link circuit, a recall relay for con necting a circuit interrupter to said answeringsignal, a second relay for connecting said circuit interrupter to said calling signal, a third relay having a circuit including a contact of one of said terminals, contacts controllable by said third relay controlling circuits for said first and second relays, and a locking circuit for each of said firstand second relays, said automatic electromagne'tic means controlling the initial operation of said recall relay, and'also cont-rolling the circuit of said anweri'ng signal.

'20. A telephone system includingapair of subscribers telephone lines, a link circuit provided with; an answering terminal and calling terminal for connecting said lines, automatic ringing means for'said link ,circuit, an answering supervisory signal and a calling supervisory signal for said link circuit, a source of interrupter current, a relay for connecting said source to said first signal, said relay also controlling the application of ringing current to a called line by said automatic ringing means, a relay for connecting said source of current to said second signal, circuits "for said relays controllable by athird relay, a locking circuit for each of said first and second relays, an operators telephone, and operator-controlled electromagnetic means for connecting the operators telephone to the link circuit when answering a'recall. I

21. A telephone system including a pair of subscribers telephone lines, a link circuit provided with an answering terminal and a calling terminal for connecting said lines, an operators telephone for'said link circuit but normally disconnecting therefrom, automatic electromagnetic means for connecting and disconnecting said opefators telephone and said link circuit, an answering supervisory signal and a calling supervisory signal for said link circuit, a source of interrupter current, a relay for connecting said source to said first signal, a relay for connecting sald source of currentto said second f signal, and automatic ringing means for slgnaling the called one of said subscribers, said automatic ringing means controlled by said first relay for disconnecting saidringing means from the called line should the calling subscriber abandon the call before answered: 7

22. A. telephone system including a calling and a called subscribers line, a link circuit for-connecting said lines, an operators telephone for said link circuit but normally disconnected therefrom, automatic electromag netic means for connecting and disconnecting said operators telephone and said link circuit, automatic ringing means for said link circuit for signaling the. called oneof said subscribers, an answering supervisory signal, means controlled by the calling subscriber for automatically flashing said signal, said means also operative to disconnect said ringing means from said link circuit should the calling subscriber abandon the call prior to a response by the called subscriber, a calling supervisory signal, and means controlled by the called subscriber for automatically flashing saidcalling signal. a, 1

A telephone system including a call ing and a called subscribers line, a link circuit for connecting said lines, automatic ringing means for said link circuit for signaling the called one of said subscribers, an

answering supervisory signal, means controlled by the calling subscriber for auto matically flashing said signal, a calling supervisory signal, and means controlled by the called subscriber for automatically flashcontacts of said second means and said last means so that ringing current may be disconnected from said link circuit by the calling or the called subscriber.

'24. A telephone system including afcalling subscribers telephone line and a called subscribers telephone line, a link circuit for connecting said lines, automatic ringing means for said link circuit, operator-coir trolled means for asociating said ringing means with the called subscribers line,calling subscriber-controlled means for disassociating said ringing means from said called subscribers line, a signal for said link circuit, a supervisory relay for said link circuit controlled by said calling subscriber, a supervisory; relay for said link circuit controllable by said called subscriber, means for automatically flashing said signal, said means being controllable by both of said supervisory relays, the said supervisory signal rendered effective to automatically flash only when said calling subsriber control means are operated to disassociate said ringing means from said calling subscribers line or tosignal for a disconnection or a recall. 7

25. telephone exchange systeminoluding telephone lines extending from substations to an exchange, link connectors for connecting said lines, automatic electromagnetic means individual to said link connectors for preventing more than one link connector from being operatively connected to the same telephone line at the same time, apparatus at said substations for signaling an exchange operator and having normal and abnormal conditions for said apparatus, a visual signal device individual to each of said link connectors, means to cause said: device to indicate a recall or a disconnect; means, operative during the time a link connector remains connected to a calling and a called line whereby a single change from abnormal to normal condition of said apparatus at a substation of said called line 120 operates said device'to indicate a disconnect and the subsequent single change from normal to abnormal condition of said apparatus operates said device to indicate a recall and means whereby a single change from abnor- 125 ing mlephone lines extending from substa- 130 tions to an exchange, link connectors for connecting said lines, automatic electromagnetic means individual to said link connectors for preventing more than one link connector from being operatively connected to the same telephone line at the same time, apparatus at said substations for signaling an exchange operator and having normal and abnormal conditions for said apparatus, a recall signal circuit, a supervisory relay and two other relays for each of said link connectors; means, operative during the time a link connector is connected to a called line, whereby a change from normal to abnormal condition of said apparatus at a substation of said line energizes said supervisory relay, thereby energizing one of said other relays; means other than said supervisory relay,'for thereafter maintaining said relay energized during said connection; means, whereby the subsequent change from abnormal to normal conditions of said apparatus de-energizes said supervisory relay and by means of said other relay energizes the third of said relays; means, other than said supervisory relay, for thereafter maintaining said third relay energized during said connection; means, including said third mentioned relay, whereby the re-energization of said. supervisory relay by the subsequent change from normal to abnormal condition of said apparatus closes said recall signal circuit; and manually operated exchange means, whereby said second and third mentioned relays may be de energi'zed during an established connection with said link connector, thereby opening said recall signal circuit.

Signed by me at Chicago, in the county of Cook and State of Illinois, this 27th day of June, 1918.

CHARLES SPARKS. 

